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Mazalo
Score: 89. Good job, see comments.
Case study
Question 1: Would you call this an epidemic? Would you call it an outbreak?
Yes this is an epidemic because you have defined in your power point that epidemic is healthrelated state or event in a defined population above the expected over a given period of time. Yes
it is an outbreak.
Question 2
Review the steps of an outbreak investigation.
We have seven steps:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
Detecting a possible outbreak
Defining and finding cases
Generating hypotheses about likely sources
Testing the hypotheses
Finding the point of contamination and source of the food
Controlling an outbreak
Deciding an outbreak is over
Question 3
List the broad categories of diseases that must be considered in the differential diagnosis of an
outbreak of gastrointestinal illness.
Answer: Staphylococcus aureus, Bacillus cereus, Clostridium perfringens, Salmonella
(nontyhpoid), Pufferfish poisoning (tetrodotoxin), shigella, giardia lamblia, Escherichia coli
enterohemorrhagic (E. coli O157:H7 and, campylobacteria, Paralytic shellfish poisoning,
Ciguatoxin, Poisonous mushroom, Clostridium botulinum, Cryptosporidium parvum, Cyclospora
cayetanensis, Yersinia enterocolitica, Vibrio cholerae O1 or 0139, Rotavirus, Listeria
monocytogenes- Invasive Disease, C. Heavy metals Antimony Cadmium, Copper, Iron, Tin
and Zinc.
Question 4
In epidemiologic parlance, what is a vehicle? What is a vector? What are other modes of
transmission?
Answer
What is a vehicle? Vehicle-borne (non-living intermediary) (e.g., HIV/AIDS spread through
infected blood on used hypodermic needle)
What is a vector? A vector is an invertebrate animal (Malaria spread through mosquitoes)
What are other modes of transmission? Direct, person-to-person contact (e.g., STDs)
Fomite-borne (inanimate object) (e.g., Hepatitis A spread by a contaminated eating utensil)
Fomite is a type of vehicle.
Question 5
If you were to administer a questionnaire to the church supper participants, what information
would you collect? Group the information into categories.
Answer
Demographic: Location: where did you eat the food? How many adults were they? How many
children were they? Age group, sex.
Clinical: What time the food was consumed? At which point the discomforts start? Is there any
food left for the test? Has this happen to them before or these are new symptoms? Have them try
to take something to relive it if so what was it and what time? Did you eat something before the
church’s food if so what was it? Did you share the food with someone else beside the church and
family member if so can you give me their names?
Laboratory: is there any food left for the test?
Inform the CDC for further investigation.
Question 6
What is a line listing?
A line listing allows information about time, person, and place to be organized and
reviewed quickly. It is also a good way to keep track of different categories of cases. For
example, cases can be entered into the line listing as possible, probable or confirmed (laboratory
confirmed, clinically confirmed or both).
What is the value of a line listing? They are laboratory values collected and put in line listing.
Question 7
What is the value of an epidemic curve?
Answer: An epidemic curve is a graphic depiction of the number of outbreak cases by date of
illness onset. It is useful because it can provide information on the outbreak’s such as: Pattern of
spread, Magnitude, Outliers, Time trend, Exposure and/or disease incubation, period.
Question 8
Using the graph paper provided, graph the cases by time of onset of illness (include
appropriate labels and title). What does this graph tell you?
Most people were sick from 10:30 am the next day from what they ate on the 18 of April. From
11pm on the 18 of April, only few people experience illness. The graph has shown that most
people were ill on the next day.
Question 9
Are there any cases for which the times of onset are inconsistent with the general experience?
Yes there were cases where the times of onset are inconsistent including 9pm, 9:15pm, 9:30 pm,
10pm, 10:30 pm, 11pm and 11:30pm on the 18th of April.
How might they be explained? People digest food in different ways. Some have a delay in
digestion while others digest faster that is why one can notice different onset illness time.
Question 10
How could the data in the line listing be better presented?
The data could be better presented by putting time from the earlier onset to the last onset illness.
Question 11
Where possible, using the new line listing, calculate incubation periods and illustrate their
distribution with an appropriate graph.
8p to 12:30am=4h: 30min, 6:30 to 12:30=6hours, 7p :30 to 10:30p=3h30min, 7:30p to 2:00am=
7:30hours, 10p to 1:00am=3hrs, 7p to 11p=4hours, 10pm to 1am=3hours,
Question 12
Determine the range and median of the incubation period.
The range= largest number - smallest number=7:30-3=4h30
Median=3hours
Question 13
How does the information on incubation period, combined with the data on clinical symptoms,
help in the differential diagnosis of the illness? (If necessary, refer to attached Compendium of
Acute Foodborne Gastrointestinal Disease).
The information on incubation period combined with the data on clinical symptoms, help in the
differential diagnosis of the illness to determinate what type of disease is out breaking. Different
diseases with different incubation time.
Question 14
Using the data in the attached line listing, complete the table below. Which food is the
most likely vehicle of infection?
Food Items
Served
Number of persons who ATE
Number of persons did NOT eat
specified food
specified food
Ill Not
Ill
Total
Percent
Ill
(Attack
rate)
Ill
Baked ham
46 29
75
61.3% 29
Spinach
43 32
75
32
Mashed potato
37 37
75
Cabbage salad
28 47
75
Jello
23 52
75
Rolls
37 38
75
Brown bread
27 48
75
Milk
4
71
75
Coffee
31 44
75
Water
24 51
75
Cakes
40 35
75
Not
Ill
Total
29
29
Percent Ill
(Attack
rate)
38.7%
Attack Rate Ratio
Ice cream, vanilla
54 21
75
Ice cream,
chocolate
47 27
75
Fruit salad
6
75
69
I had misunderstanding on the table I was not sure what I was doing was right.
Question 15
Outline further investigations that should be pursued.


How many people will be affected, and will think of an outbreak to look for help.
They can also investigate what was the condition of those who cooked the meal and ice
cream.
Question 16
What control measures would you suggest?
Wash and cook food well before eat. They can use contact measure if there is stool involve or
droplet precaution if respiration, high temperature or sneezing are involved.
Question 17
Why was it important to work up this outbreak?
It was important to work up this outbreak to prevent further break.
Question 18
Refer to the steps of an outbreak investigation you listed in Question 2. How does this
investigation fit that outline?
It fits in term of researchers be able to have some elements in their hands to work with including
testing hypothesis of people who ate ice cream and who made it.